expireover segv

[Fletcher Mattox]

> } Expireover has started to seg fault.  This is tradindex, groupbasedexpire,
> } from the Feb 10 snapshot.  Something has stepped on the address of p in
> } OVERGetHeader().
> 
> Your index seems to be corrupted, since len is too large.

Yes, this was, indeed, the case.  Whenever expireover dies ungracefully,
it seems to leave the index in a corrupted state, which causes expireover
to core dump every night until the corrupted file is manually removed.
This has happened several times.